The digital video cameras, digital still cameras, and mobile devices such as gaming system in recent years are required to be operational for long time with sufficient power, resulting to increase the capacity of the lithium ion battery pack. Therefore, we have developed the compound switching charging IC with the lithium ion/lithium polymer secondary battery charging system and the DC-DC convertor function utilizing the conventional charging technology.
 <MM3539> has a built-in charging power FET, back-flow prevention diode, crystal oscillation circuit, and RTC function, which are the peripheral of the charging block, and reduced the costs for parts in the set by managing two input power supplies, the adapter and the USB.
At the same time, the WLCSP is adopted for the package, reducing the mounting area.
With the SPI communication function, in addition to providing the individual settings for the charging control voltage and current, it has expanded the freedom of the set designing by allowing various settings. As well as being compatible with the JEITA recommended battery temperature profile, it is also compatible with various battery pack specifications, and the safety is also considered.

1.	By building in the system path, it is possible to drive the system directly from the power source without reducing the battery capacity even while charging. It also has a battery support mode that will supply the shortfall when the adapter or USB power source does not have sufficient power.
2.	The system path is a load switch type of approximately 200 mΩ, and the heat generated when driving the system and charging are performed simultaneously is reduced by charging with a switching method.
3.	The parts cost and the parts mounting cost can be reduced by building in the two input power source management function for adaptor and USB, charging power FET, back-flow prevention diode, and RTC function.
4.	The consumption current during the system backup is reduced by adopting the charge and discharge function of the button type lithium battery.
5.	Individual setting of the charge control voltage and current is possible by using the SPI communication. It is possible to modify the temperature point and charging timer in the JEITA battery temperature profile, LED blinking frequency, etc.
6.	It has a built-in ADC, and the battery voltage is monitored in 10 mV steps. It is possible for fine setting of battery temperature in approximately 1ºC steps.
7.	It has a built-in current limiting function that is necessary when using USB as a power source.

Recommended power source voltage range	ADP: 4.2 to 5.5 V USB: 2.8 to 5.5 V
Consumption current	ADP/USB mode: 1.1 mA typ. BAT mode: 180 μA typ. COIN mode: 0.65 μA typ.
Input low voltage protection detection	ADP: 4.2 V typ. USB: 2.8 V typ.
Input overvoltage protection detection	5.7 V typ.
Input overcurrent protection detection	2.5 A typ.
Battery voltage control	4.2 V (can be changed by the SPI communication)
Rapid charging current	Maximum 1.5 A (can be changed by the SPI communication)
Rapid charging timer	Maximum 24 hours (can be changed by the SPI communication)
ADC precision	±3 LSB
Package	WLCSP
External dimensions	3.47 X 3.47 X 0.64 (unit:mm)